The iliacus muscle is a large, triangular muscle located in the lateral aspect of the pelvis. It is one of the main muscles responsible for flexing the hip joint, and is important for activities such as walking, running, and climbing stairs. The iliacus muscle originates at the iliac fossa, a depression in the lateral aspect of the pelvis, and then inserts at the lesser trochanter of the femur, a bony landmark on the upper thigh bone.

In terms of function, the iliacus muscle is one of the primary muscles responsible for flexing the hip joint. This movement is important for activities such as walking, running, and climbing stairs, as it allows the leg to swing forwards and clear the ground. The iliacus muscle also plays a role in rotating the hip joint, which is important for maintaining balance and preventing falls.

In terms of daily uses, the iliacus muscle is active whenever we stand, walk, or perform any other activity that involves flexion of the hip joint. It is also used when we climb stairs, rise from a seated position, or perform movements that require rotation of the hip joint, such as side lunges or lateral leg lifts.